Catalyst for purification of aromatic acids

ABSTRACT

One aspect of the invention relates to a catalyst composite containing an extruded catalyst support containing an extruded activated carbonaceous material having specifically a defined pore structure. For example, the extruded activated carbonaceous material may have pores wherein at least about 40% of total Hg porosity occurs in pores having a diameter of about 200 Å and larger. Alternatively the extruded activated carbonaceous material may have a first set of pores having a pore diameter of at least about 40 Å and at most about 100 Å with a porosity of at least about 0.15 cc/g, and a second set of pores having a pore diameter of at least about 5,000 Å and at most about 20,000 Å with a porosity of at least about 0.3 cc/g.

RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/036,822filed Dec. 21, 2001, now U.S. Pat. No. 6,706,658 which is herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention generally relates to catalyst compositescontaining extruded catalyst supports, and methods of making andemploying the catalyst composites. The present invention particularlyrelates to catalyst materials and methods associated with thepurification of terephthalic acid.

BACKGROUND OF THE INVENTION

Catalytic processes are indispensable in the chemical industry.Frequently, catalytic processes employ a catalyst that is incorporatedon a support. Effective use of the catalyst often corresponds to thequality of the catalyst support. Poor quality catalyst supports, due toat least one of physical degradation, chemical degradation, undesirableproperties, and inconsistent properties, limit the effectiveness ofcatalysts incorporated therein. Conditions such as high temperatures,high pressures, and high or low pH environments present challenges tothe integrity of catalyst supports.

For example, conventional catalyst composites for the purification ofterephthalic acid by the Amoco mid-continent process (PTA catalysts) arecomposed of palladium-supported on granular 4×8 mesh carbon. Thesecatalyst composites are designed to remove the two major impuritiespresent in crude terephtahlic acid; namely yellow color and 4-carboxybenzaldehyde (4-CBA).

Carbon is the preferred support material for conventional PTA catalystsbecause it is essentially the only readily available material that cansimultaneously yield an effective catalyst for color removal, 4-carboxybenzaldehyde removal, and also withstand the extremely corrosiveenvironment of the terephthalic acid purification process. Althoughconventional carbon supported PTA catalysts have been used extensivelyover the past 20 years, such catalyst composites suffer from severaldisadvantages. These disadvantages include: highly irregular shapesleading to possible mal-distribution of liquid or gas flows in acatalytic reactor bed utilizing such catalyst composites; irregularshapes having sharp and fragile edges and corners which tend to breakoff and contaminate the PTA product with undesirable dust and blackparticles; brittleness which also leads to breakage and dust/blackparticles contaminating the PTA product; natural origin, i.e., coconutshell, which leads to non-uniformity form one growing season to anotherand consequent non-consistency of the carbon support; and being commonlyderived from nutshells, such activated carbon is highly microporous,leading to the requirement of locating all of the active catalytic metalat the surface of the particles, where it is undesirably susceptible toloss during the movement and abrasion which occurs during shipping andhandling.

Particularly problematic is the unpredictable and uncontrollable melangeof irregular shapes and sizes associated with commonly employed granularcocoanut carbon supports. Granular cocoanut carbons are also mostlymicroporous; that is, they have numerous pores having a pore diameterless than 50 Å. As a result, the catalytic metals must be located nearthe exterior edges of the supports to avoid low activity due to masstransfer resistances. However, when catalytic metals are located nearthe exterior edges of supports, they are subject to loss due tomechanical attrition and thus the catalyst support loses its activity.Catalytic metals located near the exterior edges of a support arereadily accessible to corrosion metals commonly present in reactor feedsand thus subject to deactivation.

Non-carbon catalyst supports are employed in catalytic processes inattempts to overcome the disadvantages associated with conventionalcarbon supported catalysts. Non-carbon supports include aluminasupports, silica supports, alumina-silica supports, various claysupports, titania, and zirconium supports. However, there are at leastone of two disadvantages associated with non-carbon catalyst supports;namely, that they may become weak and loose physical strength, that theyare dissolved in highly corrosive environments (such as hot aqueoussolutions of terephthalic acid) and that they have difficulties inremoving undesirable color from crude terephthalic acid.

Improved catalyst supports and catalyst composites are thereforedesired. Specifically, improved PTA catalyst supports and PTA catalystcomposites are desired to provide improved methods of purifyingterephthalic acid and improved useful lifetimes.

SUMMARY OF THE INVENTION

The present invention is designed to address at least one of andpreferably all of the above disadvantages by providing a catalystcomposite containing a composite support which is formed into shapeswith mesoporosity and macroporosity. The catalyst composites of thepresent invention enjoy an extended useful lifetime compared toconventional catalyst composites since they contain a support composedof an extruded carbonaceous material capable of withstanding harsh,corrosive reaction environments, such as those encountered in PTAcatalysis. In this connection, the catalyst composites of the presentinvention have a lower deactivation rate than conventional catalystcomposites. The catalyst composites of the present invention also enjoythe same or better activity with about 30% to about 50% by weight lessactive metal compared to conventional catalyst composites.

One aspect of the invention relates to a catalyst composite containing ametal catalyst and an extruded catalyst support containing an extrudedactivated carbonaceous material having specifically a defined porestructure. For example, the extruded activated carbonaceous material mayhave pores wherein at least about 40% of total Hg porosity occurs inpores having a diameter of about 200 Å or larger. Alternatively theextruded activated carbonaceous material may have a first set of poreshaving a pore diameter of at least about 40 Å and at most about 100 Åwith a porosity of at least about 0.15 cc/g, and a second set of poreshaving a pore diameter of at least about 5,000 Å and at most about20,000 Å with a porosity of at least about 0.3 cc/g.

Another aspect of the invention relates to a method of making a catalystcomposite involving mixing at least one carbonaceous material and aliquid to form a mixture; extruding the mixture into a shaped material;optionally drying the shaped material; heat treating the shaped materialat a temperature from about 600° C. to about 1,500° C. to provide acatalyst support, wherein the catalyst support has at least one of thetwo to four specifically a defined pore structures, and contacting aprecious metal catalyst with the catalyst support.

Yet another aspect of the invention relates to a method of purifying acrude polycarboxylic aromatic acid composition involving contacting thecrude polycarboxylic aromatic acid composition with a catalyst compositecontaining a metal catalyst and an extruded activated carbonaceousmaterial having at least one of the two to four specifically a definedpore structures. And still yet another aspect of the invention relatesto a method of purifying a crude amine composition or a crude alkynolamine composition involving contacting the crude amine composition orthe crude alkynol amine composition with a catalyst composite containinga catalyst support containing a metal catalyst and an extruded activatedcarbonaceous material having at least one of the two to fourspecifically a defined pore structures.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1 shows a graph of pore diameter distribution of conventionalgranular carbon and extruded carbon in accordance with one aspect of thepresent invention.

FIG. 2 shows a graph of pore diameter distribution of severalconventional granular carbons and several embodiments of extruded carbonin accordance with one aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the present invention involves the preparation ofcatalyst composites containing an extruded carbon catalyst support. Theextruded catalyst support is particularly suited for metal catalysts,especially palladium or platinum. The process according to the presentinvention of preparing the extruded catalyst support may involve themixing of a carbonaceous material and optional additives. A liquid ispreferably added to the mix to give a stiff dough which is then extruded(or pelletized or spheridized), optionally dried and heat treated toprovide a material having at least one of two pore structures. Afterheat treatment of the extruded and optionally dried material,impregnation with an active metal catalyst is conducted. In anotherembodiment, the present invention involves the use of a catalystcomposite in a catalytic process, such as in the purification of crudeterephthalic acid.

The extruded carbon catalyst support contains a carbonaceous material,and optionally one or more additives. The carbonaceous material may bederived from any suitable carbon source. The carbonaceous materialinitially used is an activated carbon, or a non-activated carbon thatmay be converted to activated carbon at some point during the formationof the extruded carbon catalyst support. For example, charcoal (anon-activated carbonaceous material) may be converted to activatedcarbon during the heat treatment step (subsequently described).Carbonaceous materials include activated carbon derived from coal,lignite, wood, nutshells, peat, pitches, cokes, and the like; andnon-activated carbon derived from carbon char powder (e.g. charcoal).

The carbonaceous material combined with any optional additives istypically in powder form. In one embodiment, the carbonaceous materialhas a particle size (average particle size) of less than about 100microns. In another embodiment, the carbonaceous material has a particlesize of less than about 80 microns. In yet another embodiment, thecarbonaceous material has a particle size of less than about 50 microns.In still yet another embodiment, the carbonaceous material has aparticle size of less than about 25 microns.

Carbonaceous materials are commercially available or they may be made.For example, carbonaceous materials may be derived from coal, coke, coalcoke, petroleum coke, lignite, polymeric materials, graphite, bone,wood, nut shells including coconut shells, resin wastes, lignocellulosicmaterials including pulp and paper, kernel, fruit pits, and sugar. Thesource of carbonaceous materials is not critical to the presentinvention. Consequently, another advantage associated with the presentinvention is that the source of carbonaceous materials is not critical.U.S. Pat. Nos. 3,084,394; 3,109,712; 3,171,720; 3,198,714; 3,310,611;3,387,940; 3,342,555; 3,345,440; 3,352,788; 3,446,593; 3,565,980;3,574,548; 3,626,042; 3,628,984; 3,634,569; 3,635,676; 3,663,171;3,859,421; 4,029,567; 4,082,694; 4,206,078; 4,263,268; 4,329,260;4,603,119; 4,668,496; 4,954,469; 4,987,116; describe variouscarbonaceous materials and are hereby incorporated by reference in thisregard.

The carbonaceous materials are chemically activated or non-chemicallyactivated. Chemical activating agents include one or more of alkalimetal hydroxides, alkali metal carbonates, alkali metal sulfide, alkalimetal sulfates, alkaline earth metal carbonates, alkaline earth metalchlorides, alkaline earth metal sulfates, alkaline earth metalphosphates, phosphoric acid, polyphosphoric acid, pyrophosphoric acid,zinc, chloride, sulfuric acid, and the like. Chemical activation isconducted by contacting one or more carbonaceous materials with one ormore chemical activating agents, mixing, optionally heating, optionallywashing/rinsing, and optionally drying the chemically activatedmaterial.

In one embodiment, the extruded carbon catalyst support contains about50% by weight or more and about 100% by weight or less of at least onecarbonaceous material. In another embodiment, the extruded carboncatalyst support contains about 60% by weight or more and about 99.9% byweight or less of at least one carbonaceous material. In yet anotherembodiment, the extruded carbon catalyst support contains about 70% byweight or more and about 99% by weight or less of at least onecarbonaceous material. In still yet another embodiment, the extrudedcarbon catalyst support contains about 75% by weight or more and about95% by weight or less of at least one carbonaceous material.

Extruded carbon catalyst supports are commercially available. Forexample, extruded carbon materials are available from Ceca, Norit,Westvaco, and Takeda. Alternatively, the extruded carbon catalystsupport may be made by mixing the carbonaceous material and any optionaladditives, forming the mixture into a shaped material, optionally dryingthe shaped material, and heat treating the shaped material to providethe hard, extruded carbon catalyst support. When mixing the carbonaceousmaterial and any optional additives, it is preferable to add water(and/or other liquid solvent). Tap water or deionized water may beemployed, but deionized water is preferred. Water is added to facilitatemixing and subsequent forming (for instance, extrusion), and thus it isadded in any amount suitable to facilitate mixing and subsequentforming. Since water is eventually removed in subsequent drying and heattreatment steps, the amount of water added is not critical to thepresent invention.

Nevertheless, in one embodiment, the mixture of optional additives andcarbonaceous material typically contains from about 5% to about 80% byweight water. In another embodiment, the mixture of optional additivesand carbonaceous material contains from about 10% to about 70% by weightwater. In another embodiment, the mixture of optional additives andcarbonaceous material contains from about 20% to about 60% by weightwater.

Additives include any material that facilitates mixing and subsequentforming. Additives include rheology control agents, extrusion aids,suspension agents, surfactants, low boiling organic compounds, rosinmaterials, polymeric additives, dispersing agents such as ammoniumlignosulfonates, and metal nitrates, sulfates, carbonates, phosphates,hydroxides, and oxides. Rheology control agents include celluloseethers, polyvinyl alcohols, and polyalkylene oxides. Examples ofcellulose ethers include sodium carboxymethylcellulose (CMC),hydroxyethylcellulose (HEC), methylcellulose (MC) and derivativesthereof. One commercially available cellulose ether is Methocel.Methocel, which contains water and hydroxypropylmethylcellulose etherpolymer, has a high thermal gelatin point, such as the productsdesignated as K4M and K15M available from Dow Chemical Company.Preferred polyalkylene oxides include polyethylene oxides. Extrusionaids include glycol compounds, such as polyalkylene glycols. In aspecific embodiment, polyethylene glycol, such as PEG 400 available fromUnion Carbide can be added as an extrusion aid. Generally, the glycolcompounds are dissolved in water and then added to the dry ingredients.

In one embodiment, the extruded carbon catalyst support typicallycontains from about 0.01% to about 10% by weight of at least oneadditive. In another embodiment, the extruded carbon catalyst supportcontains from about 0.1% to about 5% by weight of at least one additive.

The mixture of carbonaceous powder and any optional ingredients may bemixed well in a high shear mixer with water and a rheology controlagent, such as Methocel until a rather stiff dough is obtained. Thisdough can be extruded and formed into any suitable shape includingcylinders, cubes, stars, tri-lobes, quadra-lobes, pellets, spheres bysuitable mechanical means. In one embodiment, mixing is conducted in ahigh intensity environment, such as that supplied by a Littleford Mixeravailable from Littleford Day, Inc., Florence, Ky. Mixing is conductedfor a time sufficient so that a fine uniform mix results. In anotherembodiment, deionized water is added to the mixture during mixing in anamount to yield a stiff, dough-like material suitable for extrusion.

In one embodiment, the mixture of carbonaceous material and optionaladditives is mixed in a high intensity mixer from about 5 minutes toabout 100 minutes. In another embodiment, mixture of carbonaceousmaterial and optional additives is mixed in a high intensity mixer fromabout 10 minutes to about 60 minutes. In yet another embodiment, mixtureof carbonaceous material and optional additives is mixed in a highintensity mixer from about 15 minutes to about 40 minutes.

After mixing, the mixed material is extruded into a suitable shape. Theshape substantially corresponds to the shape of the resultant catalystsupport. In a preferred embodiment, the mixed material is extruded in acontinuous manner over a broad range of diameters and shapes. Examplesof forming or extrusion machines include extrusion molding machines,single screw extruders, twin screw extruders, coextruders, pinextruders, linear extruders, and monofilament extruders.

The extruded material is then optionally formed into any desired shape.Examples of forming machines include molding machines, tabletingmachines, rolling granulators, marumarizers, and pelletors. The shape ofthe extruded material includes spheres, tablets, cylinders, stars,tri-lobes, quadra-lobes, pellets, granules, honeycombs, and cubes. Theshapes, generally referred to as “particulate”, may have any suitablesize. However, in a preferred embodiment, the sizes of the shapes aresubstantially uniform. In another preferred embodiment, the mixedmaterial is extruded into cylindrical shapes having diameters from about1.5 mm to about 3.5 mm.

The extruded material has its components (the carbonaceous material andany optional additives) uniformly mixed therein. Uniformly mixedoptional additives and carbonaceous material in the subsequent resultantcatalyst support contributes to the advantageous properties of theresultant extruded catalyst support and resultant catalyst compositecontaining the catalyst support.

After extruding the material into a desired shape, the extruded materialis optionally dried to remove any remaining liquid (and typically toremove remaining water). Drying is conducted in at least one of adesiccator, under a vacuum (reduced pressure), and/or elevatedtemperature (baking) for a sufficient period of time to remove anyremaining liquid from the formed material. Drying the extruded materialcontributes to the attrition resistance properties of the resultantextruded carbon catalyst support.

The manner in which the extruded material is dried is not critical, butin many instances the drying conditions primarily depend upon at leastone of the dimensions of the extruded material, the shape of theextruded material and the manner in which the extruded material is held.In one embodiment, the dried extruded material contains less than about3% by weight free moisture. In another embodiment, the dried extrudedmaterial contains less than about 1% by weight free moisture. In yetanother embodiment, the dried extruded material contains less than about0.5% by weight free moisture.

In one embodiment, drying involves at least one of maintaining anelevated temperature (above about 35° C.) overnight, desiccationovernight, and under a vacuum overnight. When employing elevatedtemperatures, in one embodiment, the extruded material is heated fromabout 35° C. to about 150° C. for a time from about 5 seconds to about 6hours. In another embodiment, the extruded material is heated from about40° C. to about 110° C. for a time from about 30 seconds to about 30minutes. In yet another embodiment, the extruded material is heated fromabout 50° C. to about 90° C. for a time from about 1 minute to about 20minutes. In a preferred embodiment, the extruded material is subjectedto a ramped drying process (two step drying process), with the initialdrying temperature from about 40° C. to about 95° C., and morepreferably from about 60° C. to about 85° C., and then heated to atleast about 100° C., and more preferably at least about 110° C., tocomplete the drying process.

After drying, the extruded material is heat treated. However, in oneembodiment, the drying step may be incorporated into the heat treatmentstep by starting the heat treatment at a relatively low temperature (lowtemperatures relative to the heat treatment temperatures). The dried andextruded material is heat treated in any suitable manner to provide ahard catalyst support and to provide a catalyst support containing acarbonaceous material having properties corresponding with those ofactivated carbon (especially in embodiments where a non-activatedcarbonaceous material is employed).

In one embodiment, heat treatment involves heating the extruded materialat a temperature from about 600° C. to about 1,500° C. In anotherembodiment, heat treatment involves heating the extruded material at atemperature from about 700° C. to about 1,000° C. In yet anotherembodiment, heat treatment involves heating the extruded material at atemperature from about 800° C. to about 900° C. It is noted that thetemperature may vary within a temperature range. For example, thetemperature may be ramped or steadily increased during the length of theheat treatment.

The length of time the extruded material is heated primarily dependsupon the temperature, the contents of atmosphere, the size of theextruded material, the related equipment, and the identity of thecomponents (the specific type of carbonaceous material and the optionaladditives). In one embodiment, heat treatment involves heating theextruded material from about 15 minutes to about 5 hours. In anotherembodiment, heat treatment involves heating the extruded material fromabout 30 minutes to about 4 hours. Heating time refers to the amount oftime that the extruded material itself is at the temperature specified(and thus does not include ramping up or cooling down).

In one embodiment, the atmosphere in which the heat treatment isconducted contains at least steam or water vapor. The atmosphere mayfurther contain at least one of an inert gas, air, oxygen, and carbondioxide. Inert gases include the noble gases and nitrogen. Noble gasesinclude helium, neon, argon, krypton, and xenon. In another embodiment,the atmosphere in which the heat treatment is conducted contains atleast one of steam/water vapor and an inert gas. In this connection, inone embodiment, the heat treatment atmosphere contains a substantiallyinert atmosphere, such as from about 50% to about 100% of at least onean inert gas and from about 0% to less than about 50% of one or more ofsteam, air, oxygen, and carbon dioxide. In a preferred embodiment, theheat treatment atmosphere contains steam and nitrogen.

In one embodiment, the heat treatment atmosphere contains from about 5%to about 100% steam and from 0% to about 95% of at least one of an inertgas, air, oxygen, and carbon dioxide. In another embodiment, the heattreatment atmosphere contains from about 20% to about 95% steam and fromabout 5% to about 80% of at least one of an inert gas, air, oxygen, andcarbon dioxide. In yet another embodiment, the heat treatment atmospherecontains from about 30% to about 90% steam and from about 10% to about70% of at least one of an inert gas, air, oxygen, and carbon dioxide.

After heat treatment, the optionally dried, extruded product is cooledin any suitable manner. In one embodiment, the optionally dried,extruded product is cooled under an atmosphere containing an inert gas.

The resultant extruded carbon catalyst supports of the present inventionpossess a level of porosity is that controllable, primarily by varyingthe heat treatment parameters and by varying the relative amounts of theingredients (the carbonaceous material and the optional additives).Porosity may also be controllable or is further controllable by theamount and the type of additive, such as the rheology control agent orthe extrusion aid.

In one embodiment, the extruded carbon catalyst supports of the presentinvention have a bulk density from about 400 grams per liter to about1,000 grams per liter. In another embodiment, the extruded carboncatalyst supports have a bulk density from about 425 grams per liter toabout 750 grams per liter. In yet another embodiment, the extrudedcarbon catalyst supports have a bulk density from about 440 grams perliter to about 600 grams per liter.

Generally, the surface area of the extruded carbon catalyst supports ofthe present invention correspond to a weighted average of the surfacearea of the optional additives and carbonaceous material. In oneembodiment, the surface area of the extruded carbon catalyst supports isabout 300 m²/g or more and about 1,600 m²/g or less. In anotherembodiment, the surface area of the extruded carbon catalyst supports isabout 800 m²/g or more and about 1,400 m²/g or less.

The extruded carbon catalyst supports generally have a uniquedistribution of pore sizes that contributes to the advantages obtainedby the present invention. While not wishing to be bound by any theory,it is believed that the minimum surface area and/or distribution of poresizes in extruded carbon catalyst supports of the present inventioncontributes to improved aging (by maximizing porosity in pore sizes ofabout 200 Å or larger, such as at least about 40% porosity in pore sizesof about 200 Å or larger or at least about 38% porosity in pore sizes ofabout 1,000 Å or larger); improved HMBA/toluic acid ratios; improved CBAremoval and/or improved yellow color removal.

In one embodiment, the extruded carbon catalyst has a pore sizedistribution wherein a first set of pores containing a porosity of atleast about 0.15 cc/g have a pore diameter of at least about 40 Å and atmost about 100 Å, and a second set of pores containing a porosity of atleast about 0.3 cc/g have a pore diameter of at least about 5,000 Å andat most about 20,000 Å (Hg intrusion porosimetry, such as using aMicromeritics model AutoPore-II 9220 porosimeter in accordance with theanalysis method outlined in one or more of U.S. Pat. Nos. 5,186,746;5,316,576; and 5,591,256). In another embodiment, the extruded carboncatalyst has a pore size distribution wherein a first set of porescontaining a porosity of at least about 0.2 cc/g have a pore diameter ofat least about 40 Å and at most about 100 Å, and a second set of porescontaining a porosity of at least about 0.4 cc/g have a pore diameter ofat least about 5,000 Å and at most about 20,000 Å.

Referring to FIG. 1, the pore structure of a typical, conventionalgranular coconut carbon (Pica G202X) is compared with an extruded carbon(Takeda S2X) in accordance with one embodiment of the present invention.The pore volume distribution of the extruded carbon in accordance withthe present invention is weighted much more heavily in larger poreswhereas the conventional granular coconut carbon is weighted inrelatively small pores. For this reason, the conventional granularcoconut carbon is referred to as microporous, whereas the extrudedcarbon in accordance with the present invention may be referred tomesoporous and macroporous.

Referring to FIG. 2, the pore structure of four typical, conventionalgranular coconut carbons are compared with five different embodiments ofthe extruded carbons in accordance with the present invention. In thegraph, conventional granular coconut carbons include Granular TA-485Eavailable from Pica, Granular G202X available from Pica, Granular 206CATavailable from Barneby-Waterlink, and Granular NCA available from Pica.Extruded carbons include Extruded AC40/3 available from Ceca, ExtrudedRX3 Extra available from Norit, Extruded S2X available from Takeda,Extruded G2X available from Takeda, and Extruded C2X available fromTakeda. The pore volume distribution of the extruded carbons inaccordance with the present invention is weighted much more heavily inlarger pores whereas the conventional granular coconut carbon isweighted in relatively small pores. For example, as seen from the graph,at least about 40% of total Hg porosity occurs in pores having adiameter of about 200 Å and larger, such as about 1,000 Å and larger.

In Table 1 below, the amount (% by weight) of palladium in a catalystcomposite and corresponding 4-CBA removal rates are reported. The 4-CBAremoval rate is the ratio of the first order 4-CBA removal rate for thesubject catalyst composite divided by the first order 4-CBA removal ratefor a conventional standard catalyst composite (catalyst compositecontaining a Pica G202X support). The catalyst composites according tothe present invention (containing the Takeda C2X or Ceca AC40/3 basedcomposite) exhibit improved 4-CBA removal rates compared to a standardcatalyst composite (catalyst composite containing a Pica G202X support).

TABLE 1 catalyst support % Pd 4-CBA removal rate Takeda C2X 0.5 1.25Takeda C2X 0.35 1.11 Takeda C2X 0.25 0.95 Ceca AC40/3 0.5 1.2 CecaAC40/3 0.35 1.15 Pica G202X 0.5 1.0

In one embodiment, the extruded carbon catalyst has a pore sizedistribution wherein at least about 40% of total Hg porosity occurs inpores having a diameter of about 200 Å and larger (Hg intrusionporosimetry). In another embodiment, the extruded carbon catalyst has apore size distribution wherein at least about 38% of total Hg porosityoccurs in pores having a diameter of about 1,000 Å and larger. In yetanother embodiment, the extruded carbon catalyst has a pore sizedistribution wherein at least about 34% of total Hg porosity occurs inpores having a diameter of about 5,000 Å and larger.

In one embodiment, the extruded carbon catalyst has an HMBA/toluic acidratio at the end of a run of at least about 2.5. The HMBA/toluic acidratio at the end of a run is the ratio of 4-hydroxymethyl benzoic acidto toluic acid present at the end of a test purification reaction (inthe feed, the HMBA/toluic acid ratio is about 0.44). In anotherembodiment, the extruded carbon catalyst has an HMBA/toluic acid ratioat the end of a run of at least about 2.75. In yet another embodiment,the extruded carbon catalyst has an HMBA/toluic acid ratio at the end ofa run of at least about 3. In still yet another embodiment, the extrudedcarbon catalyst has an HMBA/toluic acid ratio at the end of a run of atleast about 3.25.

The extruded carbon catalysts of the present invention generally have alonger life compared to a conventional granular carbon catalysts. Inother words, the extruded carbon catalysts of the present inventiongenerally have a lower deactivation rate than conventional granularcarbon catalysts. For example, in one embodiment, the extruded carboncatalyst of the present invention containing 0.5% by weight metalcatalyst has about a 1.5 times or more longer life than a conventionalgranular carbon catalyst containing 0.5% by weight of the same metalcatalyst. In another embodiment, the extruded carbon catalyst of thepresent invention containing 0.5% by weight metal catalyst has about a 2times or more longer life than a conventional granular carbon catalystcontaining 0.5% by weight of the same metal catalyst.

In yet another embodiment, the extruded carbon catalyst of the presentinvention has a deactivation rate that is about 25% or more lower thanthe deactivation rate of a similarly loaded (same amount of same metalcatalyst) conventional granular carbon catalyst. In still yet anotherembodiment, the extruded carbon catalyst of the present invention has adeactivation rate that is about 50% or more lower than the deactivationrate of a similarly loaded conventional granular carbon catalyst.

Since the extruded carbon catalysts of the present invention have alower deactivation rate than similarly loaded conventional granularcarbon catalysts, the activities of the extruded carbon catalysts of thepresent invention are higher after various levels of aging compared toconventional granular carbon catalysts. In one embodiment, the extrudedcarbon catalyst of the present invention has an activity that is atleast about 1.5 times higher than a similarly loaded conventionalgranular carbon catalyst after 6 months, 12 months, or 18 months ofaging. In another embodiment, the extruded carbon catalyst of thepresent invention has an activity that is at least about 2 times higherthan a similarly loaded conventional granular carbon catalyst after 6months, 12 months, or 18 months of aging.

The extruded carbon catalysts of the present invention with low metalloading generally can perform equal to or even better than aconventional granular carbon catalysts with high metal loading. Forexample, in one embodiment, the extruded carbon catalyst of the presentinvention containing 0.25% by weight metal catalyst has an activityequal to or higher than a conventional granular carbon catalystcontaining 0.5% by weight of the same metal catalyst. In anotherembodiment, the extruded carbon catalyst of the present inventioncontaining 0.35% by weight metal catalyst has an activity equal to orhigher than a conventional granular carbon catalyst containing 0.5% byweight of the same metal catalyst.

In one embodiment, the present invention involves forming a catalyticcomposite by impregnating the extruded carbon catalyst support with asolution of at least one catalytically active metal. The impregnation iseffected by treating the extruded carbon catalyst support with anaqueous or organic solution of the desired metal or combination ofmetals in an amount sufficient to deposit at least one catalyticallyactive metal on or near the surface of the support, thereby providing acatalyst composite.

Catalytically active metals typically include precious metals. Examplesof catalytically active metals and mixture of metals include platinum,platinum and rhenium, platinum and ruthenium, platinum and tungsten,platinum and nickel, platinum and tin, platinum and iron, platinum andcopper, platinum and rhodium, platinum and lead, platinum and germanium,platinum and gold, platinum and tellurium, palladium and gold, palladiumand indium, palladium and sulfur, palladium and tellurium, palladium,palladium and rhenium, palladium and rhodium, palladium and tungsten,palladium and nickel, palladium and tin, palladium and copper, palladiumand ruthenium, palladium and lead, palladium and germanium, cobalt,rhodium, ruthenium, osmium, iridium, various combinations thereof, etc.It is to be understood that the aforementioned list of catalyticallyactive metals are only representative, and thus not limiting of the typeof metals which may be impregnated on the catalytic support surface.

The catalyst may be impregnated onto/into the extruded carbon catalystsupport in any suitable manner. For example, immersion techniques,spraying techniques, and incipient wetness techniques may be employed.In one embodiment, the amount of catalyst in the catalyst composite isfrom about 0.01% to about 30% by weight. In another embodiment, theamount of catalyst in the catalyst composite is from about 0.1% to about10% by weight. In yet another embodiment, the amount of catalyst in thecatalyst composite is from about 0.2% to about 5% by weight. In oneembodiment, the amount of the extruded carbon catalyst support in thecatalyst composite is from about 70% to about 99.99% by weight. Inanother embodiment, the amount of the extruded carbon catalyst supportin the catalyst composite is from about 90% to about 99.9% by weight. Inyet another embodiment, the amount of the extruded carbon catalystsupport in the catalyst composite is from about 95% to about 99.8% byweight.

The extruded carbon catalyst supports and catalyst composites of thepresent invention are suitable for use in catalytic processes. Catalyticprocesses where the extruded carbon catalyst supports and catalystcomposites of the present invention can be employed includehydrogenation, rearrangement, purification, dehydration,dehydrogenation, oxidation, reduction, polymerization,dehydrocylcization, reforming, hydrocracking, and isomerization. Thespecific catalytic reactions/processes are too numerous to list, but thefollowing are specific examples.

The extruded catalyst composite of the present invention is suitable foruse in purification of relatively impure or crude polycarboxylicaromatic acids, particularly crude terephthalic acid, isophthalic acid,phthalic acid and naphthalene dicarboxylic acid. The extruded catalystcomposite of the present invention is also suitable for use inpurification of amines and alkynol amines, and particularly aromaticamines, aromatic alkynol amines, aliphatic amines, and aliphatic alkynolamines.

In one embodiment, the impure polycarboxylic aromatic acid is a crudeproduct of the catalytic oxidation of an aromatic compound. Examples ofsuitable aromatic compounds include 1,2-dimethylnaphthalene;2,6-dialkyl-naphthalene; 2-acyl-6-alkylnaphthalene;2,6-dimethylnaphthalene, 2,6-diethylnaphthalene;2,6-diisopropylnaphthalene; 2-acetyl-6-methylnaphthalene;2-methyl-6-ethyl naphthalene; para-dialkylxylene; meta-dialkylxylene;and ortho-dialkylxylene; wherein the alkyl groups contain from 1 toabout 6 carbon atoms. In a preferred embodiment, the crude acid purifiedin accordance with the present invention is at least one of terephthalicacid formed by the oxidation of para-xylene, isophthalic acid formed bythe oxidation of meta-xylene and 2,6-naphthalene dicarboxylic acidformed by the oxidation of 2,6-dialkylnaphthalene (preferably2,6-dimethyl naphthalene). In another embodiment, the crudepolycarboxylic aromatic acid, such as 2,6-naphthalene dicarboxylic acid,is made by esterification to form the corresponding ester, in this casedimethyl naphthalene dicarboxylate, and then hydrolyzation to form thepolycarboxylic aromatic acid which is then purified in accordance withthe present invention.

Methods of catalytically purifying crude polycarboxylic aromatic acidsincluding terephthalic acid are known. For example, U.S. Pat. Nos.3,607,921; 3,887,613; 3,919,306; 4,260,817; 4,281,179; 4,317,923;4,394,299; 4,415,479; 4,447,646; 4,605,763; 4,629,715; 4,791,226;4,803,295; 4,808,751; 4,892,972; 4,937,378; 5,180,849; 5,362,908;5,420,344; 5,616,792; 5,723,659; 5,756,833; describe various methods ofcatalytically purifying crude polycarboxylic aromatic acids andparticularly terephthalic acid and are hereby incorporated by referencefor their teachings in this regard. Methods of catalytically purifyingcrude amines and alkynol amines, and particularly aromatic amines andaromatic alkynol amines, are known. In this connection, the catalystcomposite according to the present invention may be used in suchmethods.

In one embodiment, the catalyst composite is contacted with an aqueoussolution or relatively impure or crude terephthalic acid that includesrelatively large amounts of impurities such as 4-carboxy benzaldehydeand undesirable coloring. Such impurities are typically present inamounts up to about 10,000 parts per million parts of terephthalic acid,by weight (although higher amounts are encountered in some instances).These impurities adversely affect subsequent terephthalic acidpolymerization reactions to produce polyethylene terephthalate, as wellas cause undesirable coloring of the resulting polyethyleneterephthalatepolymers.

In this embodiment, the catalyst composite is contacted with an aqueoussolution of relatively impure or crude terephthalic acid at an elevatedtemperature and pressure in a fixed catalyst bed. The crude terephthalicacid to be purified is dissolved in water or a like polar solvent. Wateris a preferred solvent; however, other suitable polar solvents includethe relatively lower molecular weight alkyl carboxylic acids, alone oradmixed with water.

In one embodiment, the temperature during catalytic purification is fromabout 100° C. to about 350° C. In another embodiment, the temperatureduring catalytic purification is from about 225° C. to about 340° C.

The pressure primarily depends upon the temperature at which thepurification process is carried out. Inasmuch as the temperatures atwhich practical amounts of the impure terephthalic acid may be dissolvedare substantially above the normal boiling point of the polar solvent,the pressures are necessarily considerably above atmospheric pressure tomaintain the aqueous solution in liquid phase. If the reactor ishydraulically full, the reactor pressure can be controlled by the feedpumping rate. In one embodiment, the pressure during hydrogenation isfrom about 150 pounds per square inch guage (psig) to about 1600 psig.In another embodiment, the pressure during hydrogenation is from about900 psig to about 1,200 psig.

In the operating mode where process control is effected by adjusting thehydrogen partial pressure, the hydrogen partial pressure in the reactorpreferably is from about 10 psig to about 800 psig, from about 100 psigto about 600 psig, or higher, depending upon the service pressure ratingof the reactor, the degree of contamination of the impure terephthalicacid, the activity and age of the particular catalyst employed, and likeprocessing considerations. When purifying impure or crude terephthalicacid, in one embodiment, the reactor atmosphere contains from about 10%to about 40% by weight hydrogen and from about 60% to about 90% byweight water vapor. In another embodiment, when purifying impure orcrude terephthalic acid, the reactor atmosphere contains from about 15%to about 35% by weight hydrogen and from about 65% to about 85% byweight water vapor.

In the operating mode where process control is effected by adjustingdirectly the hydrogen concentration in the feed solution, the latterusually is less than saturated with respect to hydrogen and the reactoritself is hydraulically full. Thus, an adjustment of the hydrogen flowrate to the reactor will result in the desired control of hydrogenconcentration in the solution. In general, an amount of hydrogen that issufficient to effect the desired hydrogenation under the reactionconditions employed is supplied to the purification reactor.

In one embodiment, activity rates for the removal of 4-carboxybenzaldehyde with a 0.5% by weight Pd catalyst composites (made of Pd onthe extruded carbon catalyst supports) of the present invention are fromabout 1 hr⁻¹ to about 2.6 hr⁻¹. In another embodiment, activity ratesfor the removal of 4-carboxy benzaldehyde with a 0.5% by weight Pdcatalyst composites of the present invention are from about 1.1 hr⁻¹ toabout 2.2 hr⁻¹.

Color removal efficiencies for catalyst composites are measured viaultraviolet adsorption at 340 nm. In one embodiment, the catalystcomposites of the present invention remove at least about 75% of colorfrom crude terephthalic acid. In another embodiment, the catalystcomposites of the present invention remove at least about 80% of colorfrom crude terephthalic acid. In yet another embodiment, the catalystcomposites of the present invention remove at least about 90% of colorfrom crude terephthalic acid.

While the invention has been explained in relation to certainembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

1. A method of purifying a crude polycarboxylic aromatic acidcomposition, comprising: contacting the crude polycarboxylic aromaticacid composition with a catalyst composite comprising an extrudedactivated carbonaceous material comprising a first set of pores having apore diameter between 40 Å and 100 Å with a porosity between at minimumabout 0.15 cc/g and at maximum about 0.25 cc/g, and a second set ofpores having a pore diameter between 5,000 Å and 20,000 Å with aporosity of at minimum about 0.3 cc/g and at maximum about 0.6 cc/g; andpalladium.
 2. The method according to claim 1, wherein the crudepolycarboxylic aromatic acid composition comprises terephthalic acid,isophthalic acid and 2,6-naphthalene dicarboxylic acid.
 3. The methodaccording to claim 1, wherein the crude polycarboxylic aromatic acidcomposition comprises terephthalic acid and at least one of undesirablecoloring components and 4-carboxy benzaldehyde.
 4. The method accordingto claim 1, wherein the crude polycarboxylic aromatic acid compositionis contacted with the catalyst composite at a temperature from about100° C. to about 350° C. under a pressure from about 150 psig to about1,600 psig.
 5. A method of purifying a crude polycarboxylic aromaticacid composition, comprising: contacting the crude polycarboxylicaromatic acid composition with a catalyst composite comprising anextruded activated carbonaceous material having pores and wherein atminimum about 40% of total Hg porosity occurs in pores having a diameterbetween 200 Å and 1000 Å, and at minimum 34% of total Hg porosity occursin pores having a diameter of 5,000 Å and larger; and a metal catalystcomprising palladium.
 6. The method according to claim 5, wherein thecrude polycarboxylic aromatic acid composition comprises terephthalicacid, isophthalic acid and 2,6-naphthalene dicarboxylic acid.
 7. Themethod according to claim 5, wherein the crude polycarboxylic aromaticacid composition comprises terephthalic acid and at least one ofundesirable coloring components and 4-carboxy benzaldehyde.
 8. Themethod according to claim 5, wherein the crude polycarboxylic aromaticacid composition is contacted with the catalyst composite at atemperature from about 100° C. to about 350° C. under a pressure fromabout 150 psig to about 1,600 psig.
 9. The method according to claim 1,wherein the catalyst composite comprises about 70% by weight or more andabout 99.99% by weight or less of the extruded activated carbonaceousmaterial and about 0.01% by weight or more and about 30% by weight orless of the metal catalyst.
 10. The method according to claim 5, whereinthe catalyst composite comprises about 70% by weight or more and about99.99% by weight or less of the extruded activated carbonaceous materialand about 0.01% by weight or more and about 30% by weight or less of themetal catalyst.
 11. A method of purifying a crude polycarboxylicaromatic acid composition, comprising: contacting the crudepolycarboxylic aromatic acid composition with a catalyst compositecomprising an extruded catalyst support comprising an extruded activatedcarbonaceous material having pores and wherein at minimum about 38% oftotal Hg porosity occurs in pores having a diameter of about 1,000 Å andlarger, or at minimum 34% of total Hg porosity occurs in pores having adiameter of 5,000 Å and larger in the extruded activated carbonaceousmaterial; and a metal catalyst comprising palladium.
 12. The methodaccording to claim 11, wherein the catalyst composite comprises about70% by weight or more and about 99.99% by weight or less of the extrudedactivated carbonaceous material and about 0.01% by weight or more andabout 30% by weight or less of the metal catalyst.
 13. The methodaccording to claim 11, wherein the crude polycarboxylic aromatic acidcomposition comprises terephthalic acid, isophthalic acid and2,6-naphthalene dicarboxylic acid.
 14. The method according to claim 11,wherein the crude polycarboxylic aromatic acid composition comprisesterephthalic acid and at least one of undesirable coloring componentsand 4-carboxy benzaldehyde.
 15. The method according to claim 11,wherein the crude polycarboxylic aromatic acid composition is contactedwith the catalyst composite at a temperature from about 100° C. to about350° C. under a pressure from about 150 psig to about 1,600 psig.